Don't worry yourself too much, it could be something as simple as him missing a box that needed to be signed on his paperwork, and it needs to be completed and re- submitted.
I reccomend that you telephone, or better still visit, the office tomorrow morning and find out just what the problem is for certain. Speculation now can only get you even more worked up, and like I said it may be, amongst many possible reasons, something as trivial as paperwork being incorrectly filled out.